I apologize for my absence. I’ve had little on my mind except finishing my book on the Golden State Killer.

I got some flak for giving him that name. The displeased felt that sounded too glamorous, like he was a Hollywood star. But as my research takes me across California the more I feel the moniker, with its jarring juxtaposition, is apt. His swath of violence extended from the state capital to the central coast to a planned community in Orange County. California isn’t just a map with pushpins in this case, but a powerful presence all its own, imbuing everything with its particularities. The dense winter fog in Sacramento that he threatened to disappear into; skittish Santa Barbara deputies on night patrol ordering pot-smoking teenagers out of an avocado orchard; a friend remembering that shortly before her murder Janelle Cruz spent a day sunbathing at Laguna Beach.

The Golden State Killer attacked in communities small enough that many of the towns have online pages where locals gather to reminisce. Vivid memories abound. I learned that back in the day Goleta parents sometimes used turpentine to get the tar off their kids’ feet after a day at the beach. There are actual ruts from old stagecoaches in the rocks above Santa Barbara. One person recalled driving from Santa Barbara to Ventura back in the ‘70s with America’s “Ventura Highway” blasting on the radio.

There used to be a drive-through safari park in Irvine where an ostrich would come peck at your window.

It’s more than atmospheric details I’m after when I visit the community pages. I scroll through the memories with the hope that something useful might reveal itself, a throwaway comment about an event, or job, that might connect back to something I’ve read elsewhere. A few things are already percolating…

In the fantastic news category, one that involves another California cold case: there’s been a break in the Gypsy Hill Killings. In the first half of 1976 five young women were murdered in San Mateo County, an area south of San Francisco that includes towns like Millbrae, Daly City and Pacifica. The killings appeared to stop and the case languished for nearly forty years without any strong leads.

A remarkable turn of events reignited the case earlier this year. A Nevada inmate named Cathy Woods asked that additional forensic testing be done on evidence in her case. Woods was serving a sentence of life without parole for the Feb. 24, 1976 murder of Michelle Mitchell, 19, in Reno, Nevada. Mitchell had experienced car trouble and was last seen pushing her Volkswagen Beetle with someone’s help near the University of Nevada-Reno campus. Her body was found in a nearby garage, her hands bound and throat slashed.

Three years later Woods, a psychiatric patient in Louisiana, confessed to the crime, a confession her attorney now says was clearly false. She was tried, convicted, and spent nearly three decades in prison. Her appeal for additional forensic testing was recently granted. A cigarette butt found under Michelle Mitchell’s body was tested for DNA.

It didn’t match Cathy Woods. But it did match DNA from the unsolved Gypsy Hill murders.

That was remarkable news enough, but on Monday the FBI announced that the cigarette butt DNA had resulted in a “cold hit,” meaning it matched the DNA of a known felon in the database. That would be one Rodney Halbower, 66, an inmate at the Oregon State Penitentiary with a long rap sheet, including but not limited to violent sex crimes.

Halbower had previously been in prison in Nevada ever since he was convicted of a 1976 rape near where Mitchell was killed. He escaped in 1986 and fled to Oregon, where he committed a string of other crimes. His recent transfer from Nevada to Oregon state prison is the only reason his DNA was taken and submitted to the national database. Otherwise, as a long-time prisoner, he was hiding in Nevada’s backlog, a secret serial killer who benefited from being deemed not a high priority.

I thought of something Gary Ridgway, the Green River Killer, said when he was finally arrested.

“It was technology that caught me,” he said.

He was right. He’d slipped through multiple polygraphs and a number of police interviews. Ridgway presents as mild-mannered and unassuming, and in the vast blank space that had grown around the decades-long Green River mystery the killer loomed large, cunning and monstrous. No one could quite square the myth with the soft-spoken man.

A swab from inside Ridgeway’s cheek gave the lie to that impression. Saliva on a 40-year-old cigarette butt was the truth-teller in the Gypsy Hill Killings. But the latest news, while positive, carries other, more troubling implications. Why was a psychiatric patient with a history of delusional thinking arrested and convicted for Michelle Mitchell’s murder with little evidence?

And what can we do about the DNA backlog? The Golden State Killer case is partly responsible for why California has a more robust database than most states. But the fact remains that there are thousands of violent offenders serving sentences whose DNA samples haven’t been collected. Many of them are responsible for an untold number of unsolved crimes. They’re riding out their days, watching the clock.

It’s kind of amazing when you think about it. The scariest thing for many hardened criminals who possess hair-trigger tempers and no consciences? A small, Q-tip-like applicator called a buccal swab.

It weighs almost nothing. All that’s required is a quick, painless brush against the inside of the cheek.

But in some cases the cotton tip against the cheek is like striking a match, powerful, bringing much needed light.